1. Field of the Invention
The present invention relates to a negative dye-containing curable composition suitable for forming colored images constituting color filters used for liquid crystal display elements (CVD), solid state image pickup elements (for example, CCD and CMOS) and the like, also to a color filter produced by using the negative dye-containing curable composition and, further, to a method of producing the color filter.
2. Description of the Related Art
As methods of producing a color filter used for liquid crystal display elements and solid state image pick-up elements, a dyeing method, a printing method, an electrodepositing method and a pigment dispersion method are known.
In the pigment dispersion method, the color filter is produced by a photolithographic method using a colored radiation-sensitive composition prepared by dispersing a pigment in any one of various types of photosensitive compositions. The color filter produced by this method is stable with respect to light, heat and the like since the pigment is used. A high positional accuracy can be obtained in this method since patterning is performed by the photolithographic method and, accordingly, this method has widely been used as a method suitable for producing the color filter for a large screen and high fineness color display.
In a case in which the color filter is produced by the pigment dispersion method, the radiation-sensitive composition is first coated onto a glass substrate by using, for example, a spin coater or a roll coater and, then, dried, to thereby form a coating film. Then, colored pixels are obtained by pattern-exposing and developing the thus-formed coating film. The color filter can be obtained by repeating such operation as described above by the number of different colors.
As for the pigment dispersion method, a method which uses a negative photosensitive composition comprising an alkali-soluble resin together with a photopolymerizable monomer and a photopolymerization initiator is proposed in each of, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 2-181704, 2-199403, 5-273411 and 7-140654.
On the other hand, the color filter for the solid state image pickup element has been required to be finer in recent years. However, it is difficult to further improve resolution of the color filter according to the conventional pigment dispersion system. This is because the pigment dispersion method is not suitable for an application requiring a fine patterning such as the solid state image pickup element since color unevenness occurs due to coarse pigment particles.
In order to solve the aforementioned problems, a technique using a dye instead of the pigment is proposed in JP-A No. 6-75375. However, a problem arises that a dye-containing curable composition is generally inferior to a pigment-containing curable composition in various types of properties such as light fastness, heat resistance, solubility and coating evenness. Further, in a case in which the dye-containing curable composition is used in forming the color filter for the solid state image pickup element, since a film thickness as thin as 1.5 μm or less is particularly required, it is necessary to incorporate a large amount of dye into the curable composition and such incorporation causes other problems of an insufficient adhesion with the substrate, an insufficient curing and bleaching of the dye in an exposed portion and, then, it becomes extremely difficult to attain a good pattern forming property.